net/sunrpc/xprt.c

   1 /*
   2  *  linux/net/sunrpc/xprt.c
   3  *
   4  *  This is a generic RPC call interface supporting congestion avoidance,
   5  *  and asynchronous calls.
   6  *
   7  *  The interface works like this:
   8  *
   9  *  -   When a process places a call, it allocates a request slot if
  10  *      one is available. Otherwise, it sleeps on the backlog queue
  11  *      (xprt_reserve).
  12  *  -   Next, the caller puts together the RPC message, stuffs it into
  13  *      the request struct, and calls xprt_transmit().
  14  *  -   xprt_transmit sends the message and installs the caller on the
  15  *      transport's wait list. At the same time, if a reply is expected,
  16  *      it installs a timer that is run after the packet's timeout has
  17  *      expired.
  18  *  -   When a packet arrives, the data_ready handler walks the list of
  19  *      pending requests for that transport. If a matching XID is found, the
  20  *      caller is woken up, and the timer removed.
  21  *  -   When no reply arrives within the timeout interval, the timer is
  22  *      fired by the kernel and runs xprt_timer(). It either adjusts the
  23  *      timeout values (minor timeout) or wakes up the caller with a status
  24  *      of -ETIMEDOUT.
  25  *  -   When the caller receives a notification from RPC that a reply arrived,
  26  *      it should release the RPC slot, and process the reply.
  27  *      If the call timed out, it may choose to retry the operation by
  28  *      adjusting the initial timeout value, and simply calling rpc_call
  29  *      again.
  30  *
  31  *  Support for async RPC is done through a set of RPC-specific scheduling
  32  *  primitives that `transparently' work for processes as well as async
  33  *  tasks that rely on callbacks.
  34  *
  35  *  Copyright (C) 1995-1997, Olaf Kirch <okir@monad.swb.de>
  36  *
  37  *  Transport switch API copyright (C) 2005, Chuck Lever <cel@netapp.com>
  38  */
  39
  40 #include <linux/module.h>
  41
  42 #include <linux/types.h>
  43 #include <linux/interrupt.h>
  44 #include <linux/workqueue.h>
  45 #include <linux/net.h>
  46 #include <linux/ktime.h>
  47
  48 #include <linux/sunrpc/clnt.h>
  49 #include <linux/sunrpc/metrics.h>
  50 #include <linux/sunrpc/bc_xprt.h>
  51 #include <linux/rcupdate.h>
  52
  53 #include <trace/events/sunrpc.h>
  54
  55 #include "sunrpc.h"
  56
  57 /*
  58  * Local variables
  59  */
  60
  61 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  62 # define RPCDBG_FACILITY        RPCDBG_XPRT
  63 #endif
  64
  65 /*
  66  * Local functions
  67  */
  68 static void      xprt_init(struct rpc_xprt *xprt, struct net *net);
  69 static __be32   xprt_alloc_xid(struct rpc_xprt *xprt);
  70 static void     xprt_connect_status(struct rpc_task *task);
  71 static void      xprt_destroy(struct rpc_xprt *xprt);
  72
  73 static DEFINE_SPINLOCK(xprt_list_lock);
  74 static LIST_HEAD(xprt_list);
  75
  76 /**
  77  * xprt_register_transport - register a transport implementation
  78  * @transport: transport to register
  79  *
  80  * If a transport implementation is loaded as a kernel module, it can
  81  * call this interface to make itself known to the RPC client.
  82  *
  83  * Returns:
  84  * 0:           transport successfully registered
  85  * -EEXIST:     transport already registered
  86  * -EINVAL:     transport module being unloaded
  87  */
  88 int xprt_register_transport(struct xprt_class *transport)
  89 {
  90         struct xprt_class *t;
  91         int result;
  92
  93         result = -EEXIST;
  94         spin_lock(&xprt_list_lock);
  95         list_for_each_entry(t, &xprt_list, list) {
  96                 /* don't register the same transport class twice */
  97                 if (t->ident == transport->ident)
  98                         goto out;
  99         }
 100
 101         list_add_tail(&transport->list, &xprt_list);
 102         printk(KERN_INFO "RPC: Registered %s transport module.\n",
 103                transport->name);
 104         result = 0;
 105
 106 out:
 107         spin_unlock(&xprt_list_lock);
 108         return result;
 109 }
 110 EXPORT_SYMBOL_GPL(xprt_register_transport);
 111
 112 /**
 113  * xprt_unregister_transport - unregister a transport implementation
 114  * @transport: transport to unregister
 115  *
 116  * Returns:
 117  * 0:           transport successfully unregistered
 118  * -ENOENT:     transport never registered
 119  */
 120 int xprt_unregister_transport(struct xprt_class *transport)
 121 {
 122         struct xprt_class *t;
 123         int result;
 124
 125         result = 0;
 126         spin_lock(&xprt_list_lock);
 127         list_for_each_entry(t, &xprt_list, list) {
 128                 if (t == transport) {
 129                         printk(KERN_INFO
 130                                 "RPC: Unregistered %s transport module.\n",
 131                                 transport->name);
 132                         list_del_init(&transport->list);
 133                         goto out;
 134                 }
 135         }
 136         result = -ENOENT;
 137
 138 out:
 139         spin_unlock(&xprt_list_lock);
 140         return result;
 141 }
 142 EXPORT_SYMBOL_GPL(xprt_unregister_transport);
 143
 144 /**
 145  * xprt_load_transport - load a transport implementation
 146  * @transport_name: transport to load
 147  *
 148  * Returns:
 149  * 0:           transport successfully loaded
 150  * -ENOENT:     transport module not available
 151  */
 152 int xprt_load_transport(const char *transport_name)
 153 {
 154         struct xprt_class *t;
 155         int result;
 156
 157         result = 0;
 158         spin_lock(&xprt_list_lock);
 159         list_for_each_entry(t, &xprt_list, list) {
 160                 if (strcmp(t->name, transport_name) == 0) {
 161                         spin_unlock(&xprt_list_lock);
 162                         goto out;
 163                 }
 164         }
 165         spin_unlock(&xprt_list_lock);
 166         result = request_module("xprt%s", transport_name);
 167 out:
 168         return result;
 169 }
 170 EXPORT_SYMBOL_GPL(xprt_load_transport);
 171
 172 static void xprt_clear_locked(struct rpc_xprt *xprt)
 173 {
 174         xprt->snd_task = NULL;
 175         if (!test_bit(XPRT_CLOSE_WAIT, &xprt->state)) {
 176                 smp_mb__before_atomic();
 177                 clear_bit(XPRT_LOCKED, &xprt->state);
 178                 smp_mb__after_atomic();
 179         } else
 180                 queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 181 }
 182
 183 /**
 184  * xprt_reserve_xprt - serialize write access to transports
 185  * @task: task that is requesting access to the transport
 186  * @xprt: pointer to the target transport
 187  *
 188  * This prevents mixing the payload of separate requests, and prevents
 189  * transport connects from colliding with writes.  No congestion control
 190  * is provided.
 191  */
 192 int xprt_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
 193 {
 194         struct rpc_rqst *req = task->tk_rqstp;
 195
 196         if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
 197                 if (task == xprt->snd_task)
 198                         return 1;
 199                 goto out_sleep;
 200         }
 201         if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 202                 goto out_unlock;
 203         xprt->snd_task = task;
 204
 205         return 1;
 206
 207 out_unlock:
 208         xprt_clear_locked(xprt);
 209 out_sleep:
 210         dprintk("RPC: %5u failed to lock transport %p\n",
 211                         task->tk_pid, xprt);
 212         task->tk_timeout = RPC_IS_SOFT(task) ? req->rq_timeout : 0;
 213         task->tk_status = -EAGAIN;
 214         rpc_sleep_on(&xprt->sending, task, NULL);
 215         return 0;
 216 }
 217 EXPORT_SYMBOL_GPL(xprt_reserve_xprt);
 218
 219 static bool
 220 xprt_need_congestion_window_wait(struct rpc_xprt *xprt)
 221 {
 222         return test_bit(XPRT_CWND_WAIT, &xprt->state);
 223 }
 224
 225 static void
 226 xprt_set_congestion_window_wait(struct rpc_xprt *xprt)
 227 {
 228         if (!list_empty(&xprt->xmit_queue)) {
 229                 /* Peek at head of queue to see if it can make progress */
 230                 if (list_first_entry(&xprt->xmit_queue, struct rpc_rqst,
 231                                         rq_xmit)->rq_cong)
 232                         return;
 233         }
 234         set_bit(XPRT_CWND_WAIT, &xprt->state);
 235 }
 236
 237 static void
 238 xprt_test_and_clear_congestion_window_wait(struct rpc_xprt *xprt)
 239 {
 240         if (!RPCXPRT_CONGESTED(xprt))
 241                 clear_bit(XPRT_CWND_WAIT, &xprt->state);
 242 }
 243
 244 /*
 245  * xprt_reserve_xprt_cong - serialize write access to transports
 246  * @task: task that is requesting access to the transport
 247  *
 248  * Same as xprt_reserve_xprt, but Van Jacobson congestion control is
 249  * integrated into the decision of whether a request is allowed to be
 250  * woken up and given access to the transport.
 251  * Note that the lock is only granted if we know there are free slots.
 252  */
 253 int xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 254 {
 255         struct rpc_rqst *req = task->tk_rqstp;
 256
 257         if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
 258                 if (task == xprt->snd_task)
 259                         return 1;
 260                 goto out_sleep;
 261         }
 262         if (req == NULL) {
 263                 xprt->snd_task = task;
 264                 return 1;
 265         }
 266         if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 267                 goto out_unlock;
 268         if (!xprt_need_congestion_window_wait(xprt)) {
 269                 xprt->snd_task = task;
 270                 return 1;
 271         }
 272 out_unlock:
 273         xprt_clear_locked(xprt);
 274 out_sleep:
 275         dprintk("RPC: %5u failed to lock transport %p\n", task->tk_pid, xprt);
 276         task->tk_timeout = RPC_IS_SOFT(task) ? req->rq_timeout : 0;
 277         task->tk_status = -EAGAIN;
 278         rpc_sleep_on(&xprt->sending, task, NULL);
 279         return 0;
 280 }
 281 EXPORT_SYMBOL_GPL(xprt_reserve_xprt_cong);
 282
 283 static inline int xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
 284 {
 285         int retval;
 286
 287         if (test_bit(XPRT_LOCKED, &xprt->state) && xprt->snd_task == task)
 288                 return 1;
 289         spin_lock_bh(&xprt->transport_lock);
 290         retval = xprt->ops->reserve_xprt(xprt, task);
 291         spin_unlock_bh(&xprt->transport_lock);
 292         return retval;
 293 }
 294
 295 static bool __xprt_lock_write_func(struct rpc_task *task, void *data)
 296 {
 297         struct rpc_xprt *xprt = data;
 298
 299         xprt->snd_task = task;
 300         return true;
 301 }
 302
 303 static void __xprt_lock_write_next(struct rpc_xprt *xprt)
 304 {
 305         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 306                 return;
 307         if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 308                 goto out_unlock;
 309         if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,
 310                                 __xprt_lock_write_func, xprt))
 311                 return;
 312 out_unlock:
 313         xprt_clear_locked(xprt);
 314 }
 315
 316 static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
 317 {
 318         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 319                 return;
 320         if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
 321                 goto out_unlock;
 322         if (xprt_need_congestion_window_wait(xprt))
 323                 goto out_unlock;
 324         if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,
 325                                 __xprt_lock_write_func, xprt))
 326                 return;
 327 out_unlock:
 328         xprt_clear_locked(xprt);
 329 }
 330
 331 /**
 332  * xprt_release_xprt - allow other requests to use a transport
 333  * @xprt: transport with other tasks potentially waiting
 334  * @task: task that is releasing access to the transport
 335  *
 336  * Note that "task" can be NULL.  No congestion control is provided.
 337  */
 338 void xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)
 339 {
 340         if (xprt->snd_task == task) {
 341                 xprt_clear_locked(xprt);
 342                 __xprt_lock_write_next(xprt);
 343         }
 344 }
 345 EXPORT_SYMBOL_GPL(xprt_release_xprt);
 346
 347 /**
 348  * xprt_release_xprt_cong - allow other requests to use a transport
 349  * @xprt: transport with other tasks potentially waiting
 350  * @task: task that is releasing access to the transport
 351  *
 352  * Note that "task" can be NULL.  Another task is awoken to use the
 353  * transport if the transport's congestion window allows it.
 354  */
 355 void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 356 {
 357         if (xprt->snd_task == task) {
 358                 xprt_clear_locked(xprt);
 359                 __xprt_lock_write_next_cong(xprt);
 360         }
 361 }
 362 EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);
 363
 364 static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
 365 {
 366         if (xprt->snd_task != task)
 367                 return;
 368         spin_lock_bh(&xprt->transport_lock);
 369         xprt->ops->release_xprt(xprt, task);
 370         spin_unlock_bh(&xprt->transport_lock);
 371 }
 372
 373 /*
 374  * Van Jacobson congestion avoidance. Check if the congestion window
 375  * overflowed. Put the task to sleep if this is the case.
 376  */
 377 static int
 378 __xprt_get_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 379 {
 380         if (req->rq_cong)
 381                 return 1;
 382         dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
 383                         req->rq_task->tk_pid, xprt->cong, xprt->cwnd);
 384         if (RPCXPRT_CONGESTED(xprt)) {
 385                 xprt_set_congestion_window_wait(xprt);
 386                 return 0;
 387         }
 388         req->rq_cong = 1;
 389         xprt->cong += RPC_CWNDSCALE;
 390         return 1;
 391 }
 392
 393 /*
 394  * Adjust the congestion window, and wake up the next task
 395  * that has been sleeping due to congestion
 396  */
 397 static void
 398 __xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 399 {
 400         if (!req->rq_cong)
 401                 return;
 402         req->rq_cong = 0;
 403         xprt->cong -= RPC_CWNDSCALE;
 404         xprt_test_and_clear_congestion_window_wait(xprt);
 405         __xprt_lock_write_next_cong(xprt);
 406 }
 407
 408 /**
 409  * xprt_request_get_cong - Request congestion control credits
 410  * @xprt: pointer to transport
 411  * @req: pointer to RPC request
 412  *
 413  * Useful for transports that require congestion control.
 414  */
 415 bool
 416 xprt_request_get_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
 417 {
 418         bool ret = false;
 419
 420         if (req->rq_cong)
 421                 return true;
 422         spin_lock_bh(&xprt->transport_lock);
 423         ret = __xprt_get_cong(xprt, req) != 0;
 424         spin_unlock_bh(&xprt->transport_lock);
 425         return ret;
 426 }
 427 EXPORT_SYMBOL_GPL(xprt_request_get_cong);
 428
 429 /**
 430  * xprt_release_rqst_cong - housekeeping when request is complete
 431  * @task: RPC request that recently completed
 432  *
 433  * Useful for transports that require congestion control.
 434  */
 435 void xprt_release_rqst_cong(struct rpc_task *task)
 436 {
 437         struct rpc_rqst *req = task->tk_rqstp;
 438
 439         __xprt_put_cong(req->rq_xprt, req);
 440 }
 441 EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);
 442
 443 /*
 444  * Clear the congestion window wait flag and wake up the next
 445  * entry on xprt->sending
 446  */
 447 static void
 448 xprt_clear_congestion_window_wait(struct rpc_xprt *xprt)
 449 {
 450         if (test_and_clear_bit(XPRT_CWND_WAIT, &xprt->state)) {
 451                 spin_lock_bh(&xprt->transport_lock);
 452                 __xprt_lock_write_next_cong(xprt);
 453                 spin_unlock_bh(&xprt->transport_lock);
 454         }
 455 }
 456
 457 /**
 458  * xprt_adjust_cwnd - adjust transport congestion window
 459  * @xprt: pointer to xprt
 460  * @task: recently completed RPC request used to adjust window
 461  * @result: result code of completed RPC request
 462  *
 463  * The transport code maintains an estimate on the maximum number of out-
 464  * standing RPC requests, using a smoothed version of the congestion
 465  * avoidance implemented in 44BSD. This is basically the Van Jacobson
 466  * congestion algorithm: If a retransmit occurs, the congestion window is
 467  * halved; otherwise, it is incremented by 1/cwnd when
 468  *
 469  *      -       a reply is received and
 470  *      -       a full number of requests are outstanding and
 471  *      -       the congestion window hasn't been updated recently.
 472  */
 473 void xprt_adjust_cwnd(struct rpc_xprt *xprt, struct rpc_task *task, int result)
 474 {
 475         struct rpc_rqst *req = task->tk_rqstp;
 476         unsigned long cwnd = xprt->cwnd;
 477
 478         if (result >= 0 && cwnd <= xprt->cong) {
 479                 /* The (cwnd >> 1) term makes sure
 480                  * the result gets rounded properly. */
 481                 cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
 482                 if (cwnd > RPC_MAXCWND(xprt))
 483                         cwnd = RPC_MAXCWND(xprt);
 484                 __xprt_lock_write_next_cong(xprt);
 485         } else if (result == -ETIMEDOUT) {
 486                 cwnd >>= 1;
 487                 if (cwnd < RPC_CWNDSCALE)
 488                         cwnd = RPC_CWNDSCALE;
 489         }
 490         dprintk("RPC:       cong %ld, cwnd was %ld, now %ld\n",
 491                         xprt->cong, xprt->cwnd, cwnd);
 492         xprt->cwnd = cwnd;
 493         __xprt_put_cong(xprt, req);
 494 }
 495 EXPORT_SYMBOL_GPL(xprt_adjust_cwnd);
 496
 497 /**
 498  * xprt_wake_pending_tasks - wake all tasks on a transport's pending queue
 499  * @xprt: transport with waiting tasks
 500  * @status: result code to plant in each task before waking it
 501  *
 502  */
 503 void xprt_wake_pending_tasks(struct rpc_xprt *xprt, int status)
 504 {
 505         if (status < 0)
 506                 rpc_wake_up_status(&xprt->pending, status);
 507         else
 508                 rpc_wake_up(&xprt->pending);
 509 }
 510 EXPORT_SYMBOL_GPL(xprt_wake_pending_tasks);
 511
 512 /**
 513  * xprt_wait_for_buffer_space - wait for transport output buffer to clear
 514  * @xprt: transport
 515  *
 516  * Note that we only set the timer for the case of RPC_IS_SOFT(), since
 517  * we don't in general want to force a socket disconnection due to
 518  * an incomplete RPC call transmission.
 519  */
 520 void xprt_wait_for_buffer_space(struct rpc_xprt *xprt)
 521 {
 522         set_bit(XPRT_WRITE_SPACE, &xprt->state);
 523 }
 524 EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);
 525
 526 static bool
 527 xprt_clear_write_space_locked(struct rpc_xprt *xprt)
 528 {
 529         if (test_and_clear_bit(XPRT_WRITE_SPACE, &xprt->state)) {
 530                 __xprt_lock_write_next(xprt);
 531                 dprintk("RPC:       write space: waking waiting task on "
 532                                 "xprt %p\n", xprt);
 533                 return true;
 534         }
 535         return false;
 536 }
 537
 538 /**
 539  * xprt_write_space - wake the task waiting for transport output buffer space
 540  * @xprt: transport with waiting tasks
 541  *
 542  * Can be called in a soft IRQ context, so xprt_write_space never sleeps.
 543  */
 544 bool xprt_write_space(struct rpc_xprt *xprt)
 545 {
 546         bool ret;
 547
 548         if (!test_bit(XPRT_WRITE_SPACE, &xprt->state))
 549                 return false;
 550         spin_lock_bh(&xprt->transport_lock);
 551         ret = xprt_clear_write_space_locked(xprt);
 552         spin_unlock_bh(&xprt->transport_lock);
 553         return ret;
 554 }
 555 EXPORT_SYMBOL_GPL(xprt_write_space);
 556
 557 /**
 558  * xprt_set_retrans_timeout_def - set a request's retransmit timeout
 559  * @task: task whose timeout is to be set
 560  *
 561  * Set a request's retransmit timeout based on the transport's
 562  * default timeout parameters.  Used by transports that don't adjust
 563  * the retransmit timeout based on round-trip time estimation.
 564  */
 565 void xprt_set_retrans_timeout_def(struct rpc_task *task)
 566 {
 567         task->tk_timeout = task->tk_rqstp->rq_timeout;
 568 }
 569 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_def);
 570
 571 /**
 572  * xprt_set_retrans_timeout_rtt - set a request's retransmit timeout
 573  * @task: task whose timeout is to be set
 574  *
 575  * Set a request's retransmit timeout using the RTT estimator.
 576  */
 577 void xprt_set_retrans_timeout_rtt(struct rpc_task *task)
 578 {
 579         int timer = task->tk_msg.rpc_proc->p_timer;
 580         struct rpc_clnt *clnt = task->tk_client;
 581         struct rpc_rtt *rtt = clnt->cl_rtt;
 582         struct rpc_rqst *req = task->tk_rqstp;
 583         unsigned long max_timeout = clnt->cl_timeout->to_maxval;
 584
 585         task->tk_timeout = rpc_calc_rto(rtt, timer);
 586         task->tk_timeout <<= rpc_ntimeo(rtt, timer) + req->rq_retries;
 587         if (task->tk_timeout > max_timeout || task->tk_timeout == 0)
 588                 task->tk_timeout = max_timeout;
 589 }
 590 EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_rtt);
 591
 592 static void xprt_reset_majortimeo(struct rpc_rqst *req)
 593 {
 594         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
 595
 596         req->rq_majortimeo = req->rq_timeout;
 597         if (to->to_exponential)
 598                 req->rq_majortimeo <<= to->to_retries;
 599         else
 600                 req->rq_majortimeo += to->to_increment * to->to_retries;
 601         if (req->rq_majortimeo > to->to_maxval || req->rq_majortimeo == 0)
 602                 req->rq_majortimeo = to->to_maxval;
 603         req->rq_majortimeo += jiffies;
 604 }
 605
 606 /**
 607  * xprt_adjust_timeout - adjust timeout values for next retransmit
 608  * @req: RPC request containing parameters to use for the adjustment
 609  *
 610  */
 611 int xprt_adjust_timeout(struct rpc_rqst *req)
 612 {
 613         struct rpc_xprt *xprt = req->rq_xprt;
 614         const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;
 615         int status = 0;
 616
 617         if (time_before(jiffies, req->rq_majortimeo)) {
 618                 if (to->to_exponential)
 619                         req->rq_timeout <<= 1;
 620                 else
 621                         req->rq_timeout += to->to_increment;
 622                 if (to->to_maxval && req->rq_timeout >= to->to_maxval)
 623                         req->rq_timeout = to->to_maxval;
 624                 req->rq_retries++;
 625         } else {
 626                 req->rq_timeout = to->to_initval;
 627                 req->rq_retries = 0;
 628                 xprt_reset_majortimeo(req);
 629                 /* Reset the RTT counters == "slow start" */
 630                 spin_lock_bh(&xprt->transport_lock);
 631                 rpc_init_rtt(req->rq_task->tk_client->cl_rtt, to->to_initval);
 632                 spin_unlock_bh(&xprt->transport_lock);
 633                 status = -ETIMEDOUT;
 634         }
 635
 636         if (req->rq_timeout == 0) {
 637                 printk(KERN_WARNING "xprt_adjust_timeout: rq_timeout = 0!\n");
 638                 req->rq_timeout = 5 * HZ;
 639         }
 640         return status;
 641 }
 642
 643 static void xprt_autoclose(struct work_struct *work)
 644 {
 645         struct rpc_xprt *xprt =
 646                 container_of(work, struct rpc_xprt, task_cleanup);
 647
 648         clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 649         xprt->ops->close(xprt);
 650         xprt_release_write(xprt, NULL);
 651         wake_up_bit(&xprt->state, XPRT_LOCKED);
 652 }
 653
 654 /**
 655  * xprt_disconnect_done - mark a transport as disconnected
 656  * @xprt: transport to flag for disconnect
 657  *
 658  */
 659 void xprt_disconnect_done(struct rpc_xprt *xprt)
 660 {
 661         dprintk("RPC:       disconnected transport %p\n", xprt);
 662         spin_lock_bh(&xprt->transport_lock);
 663         xprt_clear_connected(xprt);
 664         xprt_clear_write_space_locked(xprt);
 665         xprt_wake_pending_tasks(xprt, -EAGAIN);
 666         spin_unlock_bh(&xprt->transport_lock);
 667 }
 668 EXPORT_SYMBOL_GPL(xprt_disconnect_done);
 669
 670 /**
 671  * xprt_force_disconnect - force a transport to disconnect
 672  * @xprt: transport to disconnect
 673  *
 674  */
 675 void xprt_force_disconnect(struct rpc_xprt *xprt)
 676 {
 677         /* Don't race with the test_bit() in xprt_clear_locked() */
 678         spin_lock_bh(&xprt->transport_lock);
 679         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
 680         /* Try to schedule an autoclose RPC call */
 681         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
 682                 queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 683         xprt_wake_pending_tasks(xprt, -EAGAIN);
 684         spin_unlock_bh(&xprt->transport_lock);
 685 }
 686 EXPORT_SYMBOL_GPL(xprt_force_disconnect);
 687
 688 static unsigned int
 689 xprt_connect_cookie(struct rpc_xprt *xprt)
 690 {
 691         return READ_ONCE(xprt->connect_cookie);
 692 }
 693
 694 static bool
 695 xprt_request_retransmit_after_disconnect(struct rpc_task *task)
 696 {
 697         struct rpc_rqst *req = task->tk_rqstp;
 698         struct rpc_xprt *xprt = req->rq_xprt;
 699
 700         return req->rq_connect_cookie != xprt_connect_cookie(xprt) ||
 701                 !xprt_connected(xprt);
 702 }
 703
 704 /**
 705  * xprt_conditional_disconnect - force a transport to disconnect
 706  * @xprt: transport to disconnect
 707  * @cookie: 'connection cookie'
 708  *
 709  * This attempts to break the connection if and only if 'cookie' matches
 710  * the current transport 'connection cookie'. It ensures that we don't
 711  * try to break the connection more than once when we need to retransmit
 712  * a batch of RPC requests.
 713  *
 714  */
 715 void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie)
 716 {
 717         /* Don't race with the test_bit() in xprt_clear_locked() */
 718         spin_lock_bh(&xprt->transport_lock);
 719         if (cookie != xprt->connect_cookie)
 720                 goto out;
 721         if (test_bit(XPRT_CLOSING, &xprt->state))
 722                 goto out;
 723         set_bit(XPRT_CLOSE_WAIT, &xprt->state);
 724         /* Try to schedule an autoclose RPC call */
 725         if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
 726                 queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 727         xprt_wake_pending_tasks(xprt, -EAGAIN);
 728 out:
 729         spin_unlock_bh(&xprt->transport_lock);
 730 }
 731
 732 static bool
 733 xprt_has_timer(const struct rpc_xprt *xprt)
 734 {
 735         return xprt->idle_timeout != 0;
 736 }
 737
 738 static void
 739 xprt_schedule_autodisconnect(struct rpc_xprt *xprt)
 740         __must_hold(&xprt->transport_lock)
 741 {
 742         if (RB_EMPTY_ROOT(&xprt->recv_queue) && xprt_has_timer(xprt))
 743                 mod_timer(&xprt->timer, xprt->last_used + xprt->idle_timeout);
 744 }
 745
 746 static void
 747 xprt_init_autodisconnect(struct timer_list *t)
 748 {
 749         struct rpc_xprt *xprt = from_timer(xprt, t, timer);
 750
 751         spin_lock(&xprt->transport_lock);
 752         if (!RB_EMPTY_ROOT(&xprt->recv_queue))
 753                 goto out_abort;
 754         /* Reset xprt->last_used to avoid connect/autodisconnect cycling */
 755         xprt->last_used = jiffies;
 756         if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
 757                 goto out_abort;
 758         spin_unlock(&xprt->transport_lock);
 759         queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 760         return;
 761 out_abort:
 762         spin_unlock(&xprt->transport_lock);
 763 }
 764
 765 bool xprt_lock_connect(struct rpc_xprt *xprt,
 766                 struct rpc_task *task,
 767                 void *cookie)
 768 {
 769         bool ret = false;
 770
 771         spin_lock_bh(&xprt->transport_lock);
 772         if (!test_bit(XPRT_LOCKED, &xprt->state))
 773                 goto out;
 774         if (xprt->snd_task != task)
 775                 goto out;
 776         xprt->snd_task = cookie;
 777         ret = true;
 778 out:
 779         spin_unlock_bh(&xprt->transport_lock);
 780         return ret;
 781 }
 782
 783 void xprt_unlock_connect(struct rpc_xprt *xprt, void *cookie)
 784 {
 785         spin_lock_bh(&xprt->transport_lock);
 786         if (xprt->snd_task != cookie)
 787                 goto out;
 788         if (!test_bit(XPRT_LOCKED, &xprt->state))
 789                 goto out;
 790         xprt->snd_task =NULL;
 791         xprt->ops->release_xprt(xprt, NULL);
 792         xprt_schedule_autodisconnect(xprt);
 793 out:
 794         spin_unlock_bh(&xprt->transport_lock);
 795         wake_up_bit(&xprt->state, XPRT_LOCKED);
 796 }
 797
 798 /**
 799  * xprt_connect - schedule a transport connect operation
 800  * @task: RPC task that is requesting the connect
 801  *
 802  */
 803 void xprt_connect(struct rpc_task *task)
 804 {
 805         struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
 806
 807         dprintk("RPC: %5u xprt_connect xprt %p %s connected\n", task->tk_pid,
 808                         xprt, (xprt_connected(xprt) ? "is" : "is not"));
 809
 810         if (!xprt_bound(xprt)) {
 811                 task->tk_status = -EAGAIN;
 812                 return;
 813         }
 814         if (!xprt_lock_write(xprt, task))
 815                 return;
 816
 817         if (test_and_clear_bit(XPRT_CLOSE_WAIT, &xprt->state))
 818                 xprt->ops->close(xprt);
 819
 820         if (!xprt_connected(xprt)) {
 821                 task->tk_timeout = task->tk_rqstp->rq_timeout;
 822                 task->tk_rqstp->rq_connect_cookie = xprt->connect_cookie;
 823                 rpc_sleep_on(&xprt->pending, task, xprt_connect_status);
 824
 825                 if (test_bit(XPRT_CLOSING, &xprt->state))
 826                         return;
 827                 if (xprt_test_and_set_connecting(xprt))
 828                         return;
 829                 xprt->stat.connect_start = jiffies;
 830                 xprt->ops->connect(xprt, task);
 831         }
 832         xprt_release_write(xprt, task);
 833 }
 834
 835 static void xprt_connect_status(struct rpc_task *task)
 836 {
 837         struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
 838
 839         if (task->tk_status == 0) {
 840                 xprt->stat.connect_count++;
 841                 xprt->stat.connect_time += (long)jiffies - xprt->stat.connect_start;
 842                 dprintk("RPC: %5u xprt_connect_status: connection established\n",
 843                                 task->tk_pid);
 844                 return;
 845         }
 846
 847         switch (task->tk_status) {
 848         case -ECONNREFUSED:
 849         case -ECONNRESET:
 850         case -ECONNABORTED:
 851         case -ENETUNREACH:
 852         case -EHOSTUNREACH:
 853         case -EPIPE:
 854         case -EAGAIN:
 855                 dprintk("RPC: %5u xprt_connect_status: retrying\n", task->tk_pid);
 856                 break;
 857         case -ETIMEDOUT:
 858                 dprintk("RPC: %5u xprt_connect_status: connect attempt timed "
 859                                 "out\n", task->tk_pid);
 860                 break;
 861         default:
 862                 dprintk("RPC: %5u xprt_connect_status: error %d connecting to "
 863                                 "server %s\n", task->tk_pid, -task->tk_status,
 864                                 xprt->servername);
 865                 task->tk_status = -EIO;
 866         }
 867 }
 868
 869 enum xprt_xid_rb_cmp {
 870         XID_RB_EQUAL,
 871         XID_RB_LEFT,
 872         XID_RB_RIGHT,
 873 };
 874 static enum xprt_xid_rb_cmp
 875 xprt_xid_cmp(__be32 xid1, __be32 xid2)
 876 {
 877         if (xid1 == xid2)
 878                 return XID_RB_EQUAL;
 879         if ((__force u32)xid1 < (__force u32)xid2)
 880                 return XID_RB_LEFT;
 881         return XID_RB_RIGHT;
 882 }
 883
 884 static struct rpc_rqst *
 885 xprt_request_rb_find(struct rpc_xprt *xprt, __be32 xid)
 886 {
 887         struct rb_node *n = xprt->recv_queue.rb_node;
 888         struct rpc_rqst *req;
 889
 890         while (n != NULL) {
 891                 req = rb_entry(n, struct rpc_rqst, rq_recv);
 892                 switch (xprt_xid_cmp(xid, req->rq_xid)) {
 893                 case XID_RB_LEFT:
 894                         n = n->rb_left;
 895                         break;
 896                 case XID_RB_RIGHT:
 897                         n = n->rb_right;
 898                         break;
 899                 case XID_RB_EQUAL:
 900                         return req;
 901                 }
 902         }
 903         return NULL;
 904 }
 905
 906 static void
 907 xprt_request_rb_insert(struct rpc_xprt *xprt, struct rpc_rqst *new)
 908 {
 909         struct rb_node **p = &xprt->recv_queue.rb_node;
 910         struct rb_node *n = NULL;
 911         struct rpc_rqst *req;
 912
 913         while (*p != NULL) {
 914                 n = *p;
 915                 req = rb_entry(n, struct rpc_rqst, rq_recv);
 916                 switch(xprt_xid_cmp(new->rq_xid, req->rq_xid)) {
 917                 case XID_RB_LEFT:
 918                         p = &n->rb_left;
 919                         break;
 920                 case XID_RB_RIGHT:
 921                         p = &n->rb_right;
 922                         break;
 923                 case XID_RB_EQUAL:
 924                         WARN_ON_ONCE(new != req);
 925                         return;
 926                 }
 927         }
 928         rb_link_node(&new->rq_recv, n, p);
 929         rb_insert_color(&new->rq_recv, &xprt->recv_queue);
 930 }
 931
 932 static void
 933 xprt_request_rb_remove(struct rpc_xprt *xprt, struct rpc_rqst *req)
 934 {
 935         rb_erase(&req->rq_recv, &xprt->recv_queue);
 936 }
 937
 938 /**
 939  * xprt_lookup_rqst - find an RPC request corresponding to an XID
 940  * @xprt: transport on which the original request was transmitted
 941  * @xid: RPC XID of incoming reply
 942  *
 943  * Caller holds xprt->queue_lock.
 944  */
 945 struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
 946 {
 947         struct rpc_rqst *entry;
 948
 949         entry = xprt_request_rb_find(xprt, xid);
 950         if (entry != NULL) {
 951                 trace_xprt_lookup_rqst(xprt, xid, 0);
 952                 entry->rq_rtt = ktime_sub(ktime_get(), entry->rq_xtime);
 953                 return entry;
 954         }
 955
 956         dprintk("RPC:       xprt_lookup_rqst did not find xid %08x\n",
 957                         ntohl(xid));
 958         trace_xprt_lookup_rqst(xprt, xid, -ENOENT);
 959         xprt->stat.bad_xids++;
 960         return NULL;
 961 }
 962 EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
 963
 964 static bool
 965 xprt_is_pinned_rqst(struct rpc_rqst *req)
 966 {
 967         return atomic_read(&req->rq_pin) != 0;
 968 }
 969
 970 /**
 971  * xprt_pin_rqst - Pin a request on the transport receive list
 972  * @req: Request to pin
 973  *
 974  * Caller must ensure this is atomic with the call to xprt_lookup_rqst()
 975  * so should be holding the xprt receive lock.
 976  */
 977 void xprt_pin_rqst(struct rpc_rqst *req)
 978 {
 979         atomic_inc(&req->rq_pin);
 980 }
 981 EXPORT_SYMBOL_GPL(xprt_pin_rqst);
 982
 983 /**
 984  * xprt_unpin_rqst - Unpin a request on the transport receive list
 985  * @req: Request to pin
 986  *
 987  * Caller should be holding the xprt receive lock.
 988  */
 989 void xprt_unpin_rqst(struct rpc_rqst *req)
 990 {
 991         if (!test_bit(RPC_TASK_MSG_PIN_WAIT, &req->rq_task->tk_runstate)) {
 992                 atomic_dec(&req->rq_pin);
 993                 return;
 994         }
 995         if (atomic_dec_and_test(&req->rq_pin))
 996                 wake_up_var(&req->rq_pin);
 997 }
 998 EXPORT_SYMBOL_GPL(xprt_unpin_rqst);
 999
1000 static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
1001 {
1002         wait_var_event(&req->rq_pin, !xprt_is_pinned_rqst(req));
1003 }
1004
1005 static bool
1006 xprt_request_data_received(struct rpc_task *task)
1007 {
1008         return !test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) &&
1009                 READ_ONCE(task->tk_rqstp->rq_reply_bytes_recvd) != 0;
1010 }
1011
1012 static bool
1013 xprt_request_need_enqueue_receive(struct rpc_task *task, struct rpc_rqst *req)
1014 {
1015         return !test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) &&
1016                 READ_ONCE(task->tk_rqstp->rq_reply_bytes_recvd) == 0;
1017 }
1018
1019 /**
1020  * xprt_request_enqueue_receive - Add an request to the receive queue
1021  * @task: RPC task
1022  *
1023  */
1024 void
1025 xprt_request_enqueue_receive(struct rpc_task *task)
1026 {
1027         struct rpc_rqst *req = task->tk_rqstp;
1028         struct rpc_xprt *xprt = req->rq_xprt;
1029
1030         if (!xprt_request_need_enqueue_receive(task, req))
1031                 return;
1032         spin_lock(&xprt->queue_lock);
1033
1034         /* Update the softirq receive buffer */
1035         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
1036                         sizeof(req->rq_private_buf));
1037
1038         /* Add request to the receive list */
1039         xprt_request_rb_insert(xprt, req);
1040         set_bit(RPC_TASK_NEED_RECV, &task->tk_runstate);
1041         spin_unlock(&xprt->queue_lock);
1042
1043         xprt_reset_majortimeo(req);
1044         /* Turn off autodisconnect */
1045         del_singleshot_timer_sync(&xprt->timer);
1046 }
1047
1048 /**
1049  * xprt_request_dequeue_receive_locked - Remove a request from the receive queue
1050  * @task: RPC task
1051  *
1052  * Caller must hold xprt->queue_lock.
1053  */
1054 static void
1055 xprt_request_dequeue_receive_locked(struct rpc_task *task)
1056 {
1057         struct rpc_rqst *req = task->tk_rqstp;
1058
1059         if (test_and_clear_bit(RPC_TASK_NEED_RECV, &task->tk_runstate))
1060                 xprt_request_rb_remove(req->rq_xprt, req);
1061 }
1062
1063 /**
1064  * xprt_update_rtt - Update RPC RTT statistics
1065  * @task: RPC request that recently completed
1066  *
1067  * Caller holds xprt->queue_lock.
1068  */
1069 void xprt_update_rtt(struct rpc_task *task)
1070 {
1071         struct rpc_rqst *req = task->tk_rqstp;
1072         struct rpc_rtt *rtt = task->tk_client->cl_rtt;
1073         unsigned int timer = task->tk_msg.rpc_proc->p_timer;
1074         long m = usecs_to_jiffies(ktime_to_us(req->rq_rtt));
1075
1076         if (timer) {
1077                 if (req->rq_ntrans == 1)
1078                         rpc_update_rtt(rtt, timer, m);
1079                 rpc_set_timeo(rtt, timer, req->rq_ntrans - 1);
1080         }
1081 }
1082 EXPORT_SYMBOL_GPL(xprt_update_rtt);
1083
1084 /**
1085  * xprt_complete_rqst - called when reply processing is complete
1086  * @task: RPC request that recently completed
1087  * @copied: actual number of bytes received from the transport
1088  *
1089  * Caller holds xprt->queue_lock.
1090  */
1091 void xprt_complete_rqst(struct rpc_task *task, int copied)
1092 {
1093         struct rpc_rqst *req = task->tk_rqstp;
1094         struct rpc_xprt *xprt = req->rq_xprt;
1095
1096         dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
1097                         task->tk_pid, ntohl(req->rq_xid), copied);
1098         trace_xprt_complete_rqst(xprt, req->rq_xid, copied);
1099
1100         xprt->stat.recvs++;
1101
1102         req->rq_private_buf.len = copied;
1103         /* Ensure all writes are done before we update */
1104         /* req->rq_reply_bytes_recvd */
1105         smp_wmb();
1106         req->rq_reply_bytes_recvd = copied;
1107         xprt_request_dequeue_receive_locked(task);
1108         rpc_wake_up_queued_task(&xprt->pending, task);
1109 }
1110 EXPORT_SYMBOL_GPL(xprt_complete_rqst);
1111
1112 static void xprt_timer(struct rpc_task *task)
1113 {
1114         struct rpc_rqst *req = task->tk_rqstp;
1115         struct rpc_xprt *xprt = req->rq_xprt;
1116
1117         if (task->tk_status != -ETIMEDOUT)
1118                 return;
1119
1120         trace_xprt_timer(xprt, req->rq_xid, task->tk_status);
1121         if (!req->rq_reply_bytes_recvd) {
1122                 if (xprt->ops->timer)
1123                         xprt->ops->timer(xprt, task);
1124         } else
1125                 task->tk_status = 0;
1126 }
1127
1128 /**
1129  * xprt_request_wait_receive - wait for the reply to an RPC request
1130  * @task: RPC task about to send a request
1131  *
1132  */
1133 void xprt_request_wait_receive(struct rpc_task *task)
1134 {
1135         struct rpc_rqst *req = task->tk_rqstp;
1136         struct rpc_xprt *xprt = req->rq_xprt;
1137
1138         if (!test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate))
1139                 return;
1140         /*
1141          * Sleep on the pending queue if we're expecting a reply.
1142          * The spinlock ensures atomicity between the test of
1143          * req->rq_reply_bytes_recvd, and the call to rpc_sleep_on().
1144          */
1145         spin_lock(&xprt->queue_lock);
1146         if (test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate)) {
1147                 xprt->ops->set_retrans_timeout(task);
1148                 rpc_sleep_on(&xprt->pending, task, xprt_timer);
1149                 /*
1150                  * Send an extra queue wakeup call if the
1151                  * connection was dropped in case the call to
1152                  * rpc_sleep_on() raced.
1153                  */
1154                 if (xprt_request_retransmit_after_disconnect(task))
1155                         rpc_wake_up_queued_task_set_status(&xprt->pending,
1156                                         task, -ENOTCONN);
1157         }
1158         spin_unlock(&xprt->queue_lock);
1159 }
1160
1161 static bool
1162 xprt_request_need_enqueue_transmit(struct rpc_task *task, struct rpc_rqst *req)
1163 {
1164         return !test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
1165 }
1166
1167 /**
1168  * xprt_request_enqueue_transmit - queue a task for transmission
1169  * @task: pointer to rpc_task
1170  *
1171  * Add a task to the transmission queue.
1172  */
1173 void
1174 xprt_request_enqueue_transmit(struct rpc_task *task)
1175 {
1176         struct rpc_rqst *pos, *req = task->tk_rqstp;
1177         struct rpc_xprt *xprt = req->rq_xprt;
1178
1179         if (xprt_request_need_enqueue_transmit(task, req)) {
1180                 spin_lock(&xprt->queue_lock);
1181                 /*
1182                  * Requests that carry congestion control credits are added
1183                  * to the head of the list to avoid starvation issues.
1184                  */
1185                 if (req->rq_cong) {
1186                         xprt_clear_congestion_window_wait(xprt);
1187                         list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
1188                                 if (pos->rq_cong)
1189                                         continue;
1190                                 /* Note: req is added _before_ pos */
1191                                 list_add_tail(&req->rq_xmit, &pos->rq_xmit);
1192                                 INIT_LIST_HEAD(&req->rq_xmit2);
1193                                 goto out;
1194                         }
1195                 } else if (RPC_IS_SWAPPER(task)) {
1196                         list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
1197                                 if (pos->rq_cong || pos->rq_bytes_sent)
1198                                         continue;
1199                                 if (RPC_IS_SWAPPER(pos->rq_task))
1200                                         continue;
1201                                 /* Note: req is added _before_ pos */
1202                                 list_add_tail(&req->rq_xmit, &pos->rq_xmit);
1203                                 INIT_LIST_HEAD(&req->rq_xmit2);
1204                                 goto out;
1205                         }
1206                 } else {
1207                         list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
1208                                 if (pos->rq_task->tk_owner != task->tk_owner)
1209                                         continue;
1210                                 list_add_tail(&req->rq_xmit2, &pos->rq_xmit2);
1211                                 INIT_LIST_HEAD(&req->rq_xmit);
1212                                 goto out;
1213                         }
1214                 }
1215                 list_add_tail(&req->rq_xmit, &xprt->xmit_queue);
1216                 INIT_LIST_HEAD(&req->rq_xmit2);
1217 out:
1218                 set_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
1219                 spin_unlock(&xprt->queue_lock);
1220         }
1221 }
1222
1223 /**
1224  * xprt_request_dequeue_transmit_locked - remove a task from the transmission queue
1225  * @task: pointer to rpc_task
1226  *
1227  * Remove a task from the transmission queue
1228  * Caller must hold xprt->queue_lock
1229  */
1230 static void
1231 xprt_request_dequeue_transmit_locked(struct rpc_task *task)
1232 {
1233         struct rpc_rqst *req = task->tk_rqstp;
1234
1235         if (!test_and_clear_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
1236                 return;
1237         if (!list_empty(&req->rq_xmit)) {
1238                 list_del(&req->rq_xmit);
1239                 if (!list_empty(&req->rq_xmit2)) {
1240                         struct rpc_rqst *next = list_first_entry(&req->rq_xmit2,
1241                                         struct rpc_rqst, rq_xmit2);
1242                         list_del(&req->rq_xmit2);
1243                         list_add_tail(&next->rq_xmit, &next->rq_xprt->xmit_queue);
1244                 }
1245         } else
1246                 list_del(&req->rq_xmit2);
1247 }
1248
1249 /**
1250  * xprt_request_dequeue_transmit - remove a task from the transmission queue
1251  * @task: pointer to rpc_task
1252  *
1253  * Remove a task from the transmission queue
1254  */
1255 static void
1256 xprt_request_dequeue_transmit(struct rpc_task *task)
1257 {
1258         struct rpc_rqst *req = task->tk_rqstp;
1259         struct rpc_xprt *xprt = req->rq_xprt;
1260
1261         spin_lock(&xprt->queue_lock);
1262         xprt_request_dequeue_transmit_locked(task);
1263         spin_unlock(&xprt->queue_lock);
1264 }
1265
1266 /**
1267  * xprt_request_need_retransmit - Test if a task needs retransmission
1268  * @task: pointer to rpc_task
1269  *
1270  * Test for whether a connection breakage requires the task to retransmit
1271  */
1272 bool
1273 xprt_request_need_retransmit(struct rpc_task *task)
1274 {
1275         return xprt_request_retransmit_after_disconnect(task);
1276 }
1277
1278 /**
1279  * xprt_prepare_transmit - reserve the transport before sending a request
1280  * @task: RPC task about to send a request
1281  *
1282  */
1283 bool xprt_prepare_transmit(struct rpc_task *task)
1284 {
1285         struct rpc_rqst *req = task->tk_rqstp;
1286         struct rpc_xprt *xprt = req->rq_xprt;
1287
1288         dprintk("RPC: %5u xprt_prepare_transmit\n", task->tk_pid);
1289
1290         if (!xprt_lock_write(xprt, task)) {
1291                 /* Race breaker: someone may have transmitted us */
1292                 if (!test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
1293                         rpc_wake_up_queued_task_set_status(&xprt->sending,
1294                                         task, 0);
1295                 return false;
1296
1297         }
1298         return true;
1299 }
1300
1301 void xprt_end_transmit(struct rpc_task *task)
1302 {
1303         xprt_release_write(task->tk_rqstp->rq_xprt, task);
1304 }
1305
1306 /**
1307  * xprt_request_transmit - send an RPC request on a transport
1308  * @req: pointer to request to transmit
1309  * @snd_task: RPC task that owns the transport lock
1310  *
1311  * This performs the transmission of a single request.
1312  * Note that if the request is not the same as snd_task, then it
1313  * does need to be pinned.
1314  * Returns '0' on success.
1315  */
1316 static int
1317 xprt_request_transmit(struct rpc_rqst *req, struct rpc_task *snd_task)
1318 {
1319         struct rpc_xprt *xprt = req->rq_xprt;
1320         struct rpc_task *task = req->rq_task;
1321         unsigned int connect_cookie;
1322         int is_retrans = RPC_WAS_SENT(task);
1323         int status;
1324
1325         dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
1326
1327         if (!req->rq_bytes_sent) {
1328                 if (xprt_request_data_received(task)) {
1329                         status = 0;
1330                         goto out_dequeue;
1331                 }
1332                 /* Verify that our message lies in the RPCSEC_GSS window */
1333                 if (rpcauth_xmit_need_reencode(task)) {
1334                         status = -EBADMSG;
1335                         goto out_dequeue;
1336                 }
1337         }
1338
1339         /*
1340          * Update req->rq_ntrans before transmitting to avoid races with
1341          * xprt_update_rtt(), which needs to know that it is recording a
1342          * reply to the first transmission.
1343          */
1344         req->rq_ntrans++;
1345
1346         connect_cookie = xprt->connect_cookie;
1347         status = xprt->ops->send_request(req);
1348         trace_xprt_transmit(xprt, req->rq_xid, status);
1349         if (status != 0) {
1350                 req->rq_ntrans--;
1351                 return status;
1352         }
1353
1354         if (is_retrans)
1355                 task->tk_client->cl_stats->rpcretrans++;
1356
1357         xprt_inject_disconnect(xprt);
1358
1359         dprintk("RPC: %5u xmit complete\n", task->tk_pid);
1360         task->tk_flags |= RPC_TASK_SENT;
1361         spin_lock_bh(&xprt->transport_lock);
1362
1363         xprt->stat.sends++;
1364         xprt->stat.req_u += xprt->stat.sends - xprt->stat.recvs;
1365         xprt->stat.bklog_u += xprt->backlog.qlen;
1366         xprt->stat.sending_u += xprt->sending.qlen;
1367         xprt->stat.pending_u += xprt->pending.qlen;
1368         spin_unlock_bh(&xprt->transport_lock);
1369
1370         req->rq_connect_cookie = connect_cookie;
1371 out_dequeue:
1372         xprt_request_dequeue_transmit(task);
1373         rpc_wake_up_queued_task_set_status(&xprt->sending, task, status);
1374         return status;
1375 }
1376
1377 /**
1378  * xprt_transmit - send an RPC request on a transport
1379  * @task: controlling RPC task
1380  *
1381  * Attempts to drain the transmit queue. On exit, either the transport
1382  * signalled an error that needs to be handled before transmission can
1383  * resume, or @task finished transmitting, and detected that it already
1384  * received a reply.
1385  */
1386 void
1387 xprt_transmit(struct rpc_task *task)
1388 {
1389         struct rpc_rqst *next, *req = task->tk_rqstp;
1390         struct rpc_xprt *xprt = req->rq_xprt;
1391         int status;
1392
1393         spin_lock(&xprt->queue_lock);
1394         while (!list_empty(&xprt->xmit_queue)) {
1395                 next = list_first_entry(&xprt->xmit_queue,
1396                                 struct rpc_rqst, rq_xmit);
1397                 xprt_pin_rqst(next);
1398                 spin_unlock(&xprt->queue_lock);
1399                 status = xprt_request_transmit(next, task);
1400                 if (status == -EBADMSG && next != req)
1401                         status = 0;
1402                 cond_resched();
1403                 spin_lock(&xprt->queue_lock);
1404                 xprt_unpin_rqst(next);
1405                 if (status == 0) {
1406                         if (!xprt_request_data_received(task) ||
1407                             test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
1408                                 continue;
1409                 } else if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
1410                         task->tk_status = status;
1411                 break;
1412         }
1413         spin_unlock(&xprt->queue_lock);
1414 }
1415
1416 static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task)
1417 {
1418         set_bit(XPRT_CONGESTED, &xprt->state);
1419         rpc_sleep_on(&xprt->backlog, task, NULL);
1420 }
1421
1422 static void xprt_wake_up_backlog(struct rpc_xprt *xprt)
1423 {
1424         if (rpc_wake_up_next(&xprt->backlog) == NULL)
1425                 clear_bit(XPRT_CONGESTED, &xprt->state);
1426 }
1427
1428 static bool xprt_throttle_congested(struct rpc_xprt *xprt, struct rpc_task *task)
1429 {
1430         bool ret = false;
1431
1432         if (!test_bit(XPRT_CONGESTED, &xprt->state))
1433                 goto out;
1434         spin_lock(&xprt->reserve_lock);
1435         if (test_bit(XPRT_CONGESTED, &xprt->state)) {
1436                 rpc_sleep_on(&xprt->backlog, task, NULL);
1437                 ret = true;
1438         }
1439         spin_unlock(&xprt->reserve_lock);
1440 out:
1441         return ret;
1442 }
1443
1444 static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt)
1445 {
1446         struct rpc_rqst *req = ERR_PTR(-EAGAIN);
1447
1448         if (xprt->num_reqs >= xprt->max_reqs)
1449                 goto out;
1450         ++xprt->num_reqs;
1451         spin_unlock(&xprt->reserve_lock);
1452         req = kzalloc(sizeof(struct rpc_rqst), GFP_NOFS);
1453         spin_lock(&xprt->reserve_lock);
1454         if (req != NULL)
1455                 goto out;
1456         --xprt->num_reqs;
1457         req = ERR_PTR(-ENOMEM);
1458 out:
1459         return req;
1460 }
1461
1462 static bool xprt_dynamic_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
1463 {
1464         if (xprt->num_reqs > xprt->min_reqs) {
1465                 --xprt->num_reqs;
1466                 kfree(req);
1467                 return true;
1468         }
1469         return false;
1470 }
1471
1472 void xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
1473 {
1474         struct rpc_rqst *req;
1475
1476         spin_lock(&xprt->reserve_lock);
1477         if (!list_empty(&xprt->free)) {
1478                 req = list_entry(xprt->free.next, struct rpc_rqst, rq_list);
1479                 list_del(&req->rq_list);
1480                 goto out_init_req;
1481         }
1482         req = xprt_dynamic_alloc_slot(xprt);
1483         if (!IS_ERR(req))
1484                 goto out_init_req;
1485         switch (PTR_ERR(req)) {
1486         case -ENOMEM:
1487                 dprintk("RPC:       dynamic allocation of request slot "
1488                                 "failed! Retrying\n");
1489                 task->tk_status = -ENOMEM;
1490                 break;
1491         case -EAGAIN:
1492                 xprt_add_backlog(xprt, task);
1493                 dprintk("RPC:       waiting for request slot\n");
1494                 /* fall through */
1495         default:
1496                 task->tk_status = -EAGAIN;
1497         }
1498         spin_unlock(&xprt->reserve_lock);
1499         return;
1500 out_init_req:
1501         xprt->stat.max_slots = max_t(unsigned int, xprt->stat.max_slots,
1502                                      xprt->num_reqs);
1503         spin_unlock(&xprt->reserve_lock);
1504
1505         task->tk_status = 0;
1506         task->tk_rqstp = req;
1507 }
1508 EXPORT_SYMBOL_GPL(xprt_alloc_slot);
1509
1510 void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
1511 {
1512         spin_lock(&xprt->reserve_lock);
1513         if (!xprt_dynamic_free_slot(xprt, req)) {
1514                 memset(req, 0, sizeof(*req));   /* mark unused */
1515                 list_add(&req->rq_list, &xprt->free);
1516         }
1517         xprt_wake_up_backlog(xprt);
1518         spin_unlock(&xprt->reserve_lock);
1519 }
1520 EXPORT_SYMBOL_GPL(xprt_free_slot);
1521
1522 static void xprt_free_all_slots(struct rpc_xprt *xprt)
1523 {
1524         struct rpc_rqst *req;
1525         while (!list_empty(&xprt->free)) {
1526                 req = list_first_entry(&xprt->free, struct rpc_rqst, rq_list);
1527                 list_del(&req->rq_list);
1528                 kfree(req);
1529         }
1530 }
1531
1532 struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
1533                 unsigned int num_prealloc,
1534                 unsigned int max_alloc)
1535 {
1536         struct rpc_xprt *xprt;
1537         struct rpc_rqst *req;
1538         int i;
1539
1540         xprt = kzalloc(size, GFP_KERNEL);
1541         if (xprt == NULL)
1542                 goto out;
1543
1544         xprt_init(xprt, net);
1545
1546         for (i = 0; i < num_prealloc; i++) {
1547                 req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
1548                 if (!req)
1549                         goto out_free;
1550                 list_add(&req->rq_list, &xprt->free);
1551         }
1552         if (max_alloc > num_prealloc)
1553                 xprt->max_reqs = max_alloc;
1554         else
1555                 xprt->max_reqs = num_prealloc;
1556         xprt->min_reqs = num_prealloc;
1557         xprt->num_reqs = num_prealloc;
1558
1559         return xprt;
1560
1561 out_free:
1562         xprt_free(xprt);
1563 out:
1564         return NULL;
1565 }
1566 EXPORT_SYMBOL_GPL(xprt_alloc);
1567
1568 void xprt_free(struct rpc_xprt *xprt)
1569 {
1570         put_net(xprt->xprt_net);
1571         xprt_free_all_slots(xprt);
1572         kfree_rcu(xprt, rcu);
1573 }
1574 EXPORT_SYMBOL_GPL(xprt_free);
1575
1576 static void
1577 xprt_init_connect_cookie(struct rpc_rqst *req, struct rpc_xprt *xprt)
1578 {
1579         req->rq_connect_cookie = xprt_connect_cookie(xprt) - 1;
1580 }
1581
1582 static __be32
1583 xprt_alloc_xid(struct rpc_xprt *xprt)
1584 {
1585         __be32 xid;
1586
1587         spin_lock(&xprt->reserve_lock);
1588         xid = (__force __be32)xprt->xid++;
1589         spin_unlock(&xprt->reserve_lock);
1590         return xid;
1591 }
1592
1593 static void
1594 xprt_init_xid(struct rpc_xprt *xprt)
1595 {
1596         xprt->xid = prandom_u32();
1597 }
1598
1599 static void
1600 xprt_request_init(struct rpc_task *task)
1601 {
1602         struct rpc_xprt *xprt = task->tk_xprt;
1603         struct rpc_rqst *req = task->tk_rqstp;
1604
1605         req->rq_timeout = task->tk_client->cl_timeout->to_initval;
1606         req->rq_task    = task;
1607         req->rq_xprt    = xprt;
1608         req->rq_buffer  = NULL;
1609         req->rq_xid     = xprt_alloc_xid(xprt);
1610         xprt_init_connect_cookie(req, xprt);
1611         req->rq_bytes_sent = 0;
1612         req->rq_snd_buf.len = 0;
1613         req->rq_snd_buf.buflen = 0;
1614         req->rq_rcv_buf.len = 0;
1615         req->rq_rcv_buf.buflen = 0;
1616         req->rq_release_snd_buf = NULL;
1617         xprt_reset_majortimeo(req);
1618         dprintk("RPC: %5u reserved req %p xid %08x\n", task->tk_pid,
1619                         req, ntohl(req->rq_xid));
1620 }
1621
1622 static void
1623 xprt_do_reserve(struct rpc_xprt *xprt, struct rpc_task *task)
1624 {
1625         xprt->ops->alloc_slot(xprt, task);
1626         if (task->tk_rqstp != NULL)
1627                 xprt_request_init(task);
1628 }
1629
1630 /**
1631  * xprt_reserve - allocate an RPC request slot
1632  * @task: RPC task requesting a slot allocation
1633  *
1634  * If the transport is marked as being congested, or if no more
1635  * slots are available, place the task on the transport's
1636  * backlog queue.
1637  */
1638 void xprt_reserve(struct rpc_task *task)
1639 {
1640         struct rpc_xprt *xprt = task->tk_xprt;
1641
1642         task->tk_status = 0;
1643         if (task->tk_rqstp != NULL)
1644                 return;
1645
1646         task->tk_timeout = 0;
1647         task->tk_status = -EAGAIN;
1648         if (!xprt_throttle_congested(xprt, task))
1649                 xprt_do_reserve(xprt, task);
1650 }
1651
1652 /**
1653  * xprt_retry_reserve - allocate an RPC request slot
1654  * @task: RPC task requesting a slot allocation
1655  *
1656  * If no more slots are available, place the task on the transport's
1657  * backlog queue.
1658  * Note that the only difference with xprt_reserve is that we now
1659  * ignore the value of the XPRT_CONGESTED flag.
1660  */
1661 void xprt_retry_reserve(struct rpc_task *task)
1662 {
1663         struct rpc_xprt *xprt = task->tk_xprt;
1664
1665         task->tk_status = 0;
1666         if (task->tk_rqstp != NULL)
1667                 return;
1668
1669         task->tk_timeout = 0;
1670         task->tk_status = -EAGAIN;
1671         xprt_do_reserve(xprt, task);
1672 }
1673
1674 static void
1675 xprt_request_dequeue_all(struct rpc_task *task, struct rpc_rqst *req)
1676 {
1677         struct rpc_xprt *xprt = req->rq_xprt;
1678
1679         if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate) ||
1680             test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) ||
1681             xprt_is_pinned_rqst(req)) {
1682                 spin_lock(&xprt->queue_lock);
1683                 xprt_request_dequeue_transmit_locked(task);
1684                 xprt_request_dequeue_receive_locked(task);
1685                 while (xprt_is_pinned_rqst(req)) {
1686                         set_bit(RPC_TASK_MSG_PIN_WAIT, &task->tk_runstate);
1687                         spin_unlock(&xprt->queue_lock);
1688                         xprt_wait_on_pinned_rqst(req);
1689                         spin_lock(&xprt->queue_lock);
1690                         clear_bit(RPC_TASK_MSG_PIN_WAIT, &task->tk_runstate);
1691                 }
1692                 spin_unlock(&xprt->queue_lock);
1693         }
1694 }
1695
1696 /**
1697  * xprt_release - release an RPC request slot
1698  * @task: task which is finished with the slot
1699  *
1700  */
1701 void xprt_release(struct rpc_task *task)
1702 {
1703         struct rpc_xprt *xprt;
1704         struct rpc_rqst *req = task->tk_rqstp;
1705
1706         if (req == NULL) {
1707                 if (task->tk_client) {
1708                         xprt = task->tk_xprt;
1709                         xprt_release_write(xprt, task);
1710                 }
1711                 return;
1712         }
1713
1714         xprt = req->rq_xprt;
1715         if (task->tk_ops->rpc_count_stats != NULL)
1716                 task->tk_ops->rpc_count_stats(task, task->tk_calldata);
1717         else if (task->tk_client)
1718                 rpc_count_iostats(task, task->tk_client->cl_metrics);
1719         xprt_request_dequeue_all(task, req);
1720         spin_lock_bh(&xprt->transport_lock);
1721         xprt->ops->release_xprt(xprt, task);
1722         if (xprt->ops->release_request)
1723                 xprt->ops->release_request(task);
1724         xprt->last_used = jiffies;
1725         xprt_schedule_autodisconnect(xprt);
1726         spin_unlock_bh(&xprt->transport_lock);
1727         if (req->rq_buffer)
1728                 xprt->ops->buf_free(task);
1729         xprt_inject_disconnect(xprt);
1730         if (req->rq_cred != NULL)
1731                 put_rpccred(req->rq_cred);
1732         task->tk_rqstp = NULL;
1733         if (req->rq_release_snd_buf)
1734                 req->rq_release_snd_buf(req);
1735
1736         dprintk("RPC: %5u release request %p\n", task->tk_pid, req);
1737         if (likely(!bc_prealloc(req)))
1738                 xprt->ops->free_slot(xprt, req);
1739         else
1740                 xprt_free_bc_request(req);
1741 }
1742
1743 #ifdef CONFIG_SUNRPC_BACKCHANNEL
1744 void
1745 xprt_init_bc_request(struct rpc_rqst *req, struct rpc_task *task)
1746 {
1747         struct xdr_buf *xbufp = &req->rq_snd_buf;
1748
1749         task->tk_rqstp = req;
1750         req->rq_task = task;
1751         xprt_init_connect_cookie(req, req->rq_xprt);
1752         /*
1753          * Set up the xdr_buf length.
1754          * This also indicates that the buffer is XDR encoded already.
1755          */
1756         xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
1757                 xbufp->tail[0].iov_len;
1758         req->rq_bytes_sent = 0;
1759 }
1760 #endif
1761
1762 static void xprt_init(struct rpc_xprt *xprt, struct net *net)
1763 {
1764         kref_init(&xprt->kref);
1765
1766         spin_lock_init(&xprt->transport_lock);
1767         spin_lock_init(&xprt->reserve_lock);
1768         spin_lock_init(&xprt->queue_lock);
1769
1770         INIT_LIST_HEAD(&xprt->free);
1771         xprt->recv_queue = RB_ROOT;
1772         INIT_LIST_HEAD(&xprt->xmit_queue);
1773 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
1774         spin_lock_init(&xprt->bc_pa_lock);
1775         INIT_LIST_HEAD(&xprt->bc_pa_list);
1776 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
1777         INIT_LIST_HEAD(&xprt->xprt_switch);
1778
1779         xprt->last_used = jiffies;
1780         xprt->cwnd = RPC_INITCWND;
1781         xprt->bind_index = 0;
1782
1783         rpc_init_wait_queue(&xprt->binding, "xprt_binding");
1784         rpc_init_wait_queue(&xprt->pending, "xprt_pending");
1785         rpc_init_wait_queue(&xprt->sending, "xprt_sending");
1786         rpc_init_priority_wait_queue(&xprt->backlog, "xprt_backlog");
1787
1788         xprt_init_xid(xprt);
1789
1790         xprt->xprt_net = get_net(net);
1791 }
1792
1793 /**
1794  * xprt_create_transport - create an RPC transport
1795  * @args: rpc transport creation arguments
1796  *
1797  */
1798 struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
1799 {
1800         struct rpc_xprt *xprt;
1801         struct xprt_class *t;
1802
1803         spin_lock(&xprt_list_lock);
1804         list_for_each_entry(t, &xprt_list, list) {
1805                 if (t->ident == args->ident) {
1806                         spin_unlock(&xprt_list_lock);
1807                         goto found;
1808                 }
1809         }
1810         spin_unlock(&xprt_list_lock);
1811         dprintk("RPC: transport (%d) not supported\n", args->ident);
1812         return ERR_PTR(-EIO);
1813
1814 found:
1815         xprt = t->setup(args);
1816         if (IS_ERR(xprt)) {
1817                 dprintk("RPC:       xprt_create_transport: failed, %ld\n",
1818                                 -PTR_ERR(xprt));
1819                 goto out;
1820         }
1821         if (args->flags & XPRT_CREATE_NO_IDLE_TIMEOUT)
1822                 xprt->idle_timeout = 0;
1823         INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
1824         if (xprt_has_timer(xprt))
1825                 timer_setup(&xprt->timer, xprt_init_autodisconnect, 0);
1826         else
1827                 timer_setup(&xprt->timer, NULL, 0);
1828
1829         if (strlen(args->servername) > RPC_MAXNETNAMELEN) {
1830                 xprt_destroy(xprt);
1831                 return ERR_PTR(-EINVAL);
1832         }
1833         xprt->servername = kstrdup(args->servername, GFP_KERNEL);
1834         if (xprt->servername == NULL) {
1835                 xprt_destroy(xprt);
1836                 return ERR_PTR(-ENOMEM);
1837         }
1838
1839         rpc_xprt_debugfs_register(xprt);
1840
1841         dprintk("RPC:       created transport %p with %u slots\n", xprt,
1842                         xprt->max_reqs);
1843 out:
1844         return xprt;
1845 }
1846
1847 static void xprt_destroy_cb(struct work_struct *work)
1848 {
1849         struct rpc_xprt *xprt =
1850                 container_of(work, struct rpc_xprt, task_cleanup);
1851
1852         rpc_xprt_debugfs_unregister(xprt);
1853         rpc_destroy_wait_queue(&xprt->binding);
1854         rpc_destroy_wait_queue(&xprt->pending);
1855         rpc_destroy_wait_queue(&xprt->sending);
1856         rpc_destroy_wait_queue(&xprt->backlog);
1857         kfree(xprt->servername);
1858         /*
1859          * Tear down transport state and free the rpc_xprt
1860          */
1861         xprt->ops->destroy(xprt);
1862 }
1863
1864 /**
1865  * xprt_destroy - destroy an RPC transport, killing off all requests.
1866  * @xprt: transport to destroy
1867  *
1868  */
1869 static void xprt_destroy(struct rpc_xprt *xprt)
1870 {
1871         dprintk("RPC:       destroying transport %p\n", xprt);
1872
1873         /*
1874          * Exclude transport connect/disconnect handlers and autoclose
1875          */
1876         wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE);
1877
1878         del_timer_sync(&xprt->timer);
1879
1880         /*
1881          * Destroy sockets etc from the system workqueue so they can
1882          * safely flush receive work running on rpciod.
1883          */
1884         INIT_WORK(&xprt->task_cleanup, xprt_destroy_cb);
1885         schedule_work(&xprt->task_cleanup);
1886 }
1887
1888 static void xprt_destroy_kref(struct kref *kref)
1889 {
1890         xprt_destroy(container_of(kref, struct rpc_xprt, kref));
1891 }
1892
1893 /**
1894  * xprt_get - return a reference to an RPC transport.
1895  * @xprt: pointer to the transport
1896  *
1897  */
1898 struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
1899 {
1900         if (xprt != NULL && kref_get_unless_zero(&xprt->kref))
1901                 return xprt;
1902         return NULL;
1903 }
1904 EXPORT_SYMBOL_GPL(xprt_get);
1905
1906 /**
1907  * xprt_put - release a reference to an RPC transport.
1908  * @xprt: pointer to the transport
1909  *
1910  */
1911 void xprt_put(struct rpc_xprt *xprt)
1912 {
1913         if (xprt != NULL)
1914                 kref_put(&xprt->kref, xprt_destroy_kref);
1915 }
1916 EXPORT_SYMBOL_GPL(xprt_put);